'I decided I wasn’t going to be afraid of the chamber, and I would make sure I spoke regularly' … Jo Swinson MP. Photograph: Linda Nylind for the Guardian

On the way to meet Jo Swinson I'm still unsure what to make of the Lib Dem MP's campaign for body confidence. Is this a gutsy, slightly risky move by a young woman on her way up, taking on an issue that proved calamitous for Labour in 2000, when its "body image summit" was widely ridiculed? Is it a subject simply too soft and fuzzy for the political arena? (The YMCA's website for their part of the campaign features pictures of barely clad people holding hearts saying "I love me" over their genitals, as if recently beset by Gok Wan, Trinny, Susannah and some unruly Care Bears.) Or is it an impressive example of a politician using techniques often associated with grassroots campaigners – the simple, straightforward letter of complaint – to secure surprising results?

Most importantly: is it what politicians should be focusing on right now? There's no doubt this week saw Swinson notch up another small triumph in her campaign. On Wednesday it was reported that a complaint she had made to the Advertising Standards Authority (ASA) had led to it ruling that an ad for a L'Oréal anti-wrinkle cream could never again appear in its current form. The ad showed a lovely photograph of the actor Rachel Weisz, her skin glassily, fantastically smooth. The ASA decided that although the ad didn't misrepresent the "luminosity or wrinkling" of Weisz's face, "the image had been altered in a way that substantially changed her complexion to make it appear smoother and more even", and concluded it could therefore mislead the public as to the product's performance. This came after two rulings in Swinson's favour last year – ads featuring Julia Roberts and Christy Turlington were also deemed to have been digitally enhanced, and potentially misleading – and another in 2009, when an image of Twiggy was pulled.

All perfectly laudable. No one would argue in favour of misleading adverts, few in favour of the over-enthusiastic use of airbrushing – even if trying to stem this last tide seems Sisyphean in a digital age. And yet it still feels slightly odd to see an MP focusing on this issue in the midst of an economic crisis. Body confidence obviously affects both men and women, but primarily the latter, yet when I talk to women's campaigners it doesn't seem to be at the forefront of the issues they are worried about. The Fawcett Society, the UK's leading women's rights campaign, seems more concerned about the 23-year high in women's unemployment, and the way cuts to benefits will disproportionately affect women (a fifth of female income comes from welfare payments and tax credits, compared to a tenth of male income).

Others cite this week's news that local authority cuts to the domestic violence sector have led to women being advised to sleep in Occupy camps or police stations because all the shelters are full. Body image may have seemed a pressing issue before the recession, and it is very necessary, of course, for campaigners, doctors and academics to work together on eating disorders and associated problems. But is it a priority for the political arena?

I meet Swinson in a cafe in Kennington, south London, the area where she lives with her husband, fellow Lib Dem MP Duncan Hames. She bustles in from the cold, and we get straight to talking about the campaign. I ask why she feels so strongly about this issue, and she says she feels strongly about a lot of issues. This is certainly true. There can be no doubting Swinson's commitment.

In 2005, when she was elected MP for East Dunbartonshire, the area where she grew up, Swinson was 25, the youngest MP in the House. She made a decision, she says, "that I wasn't going to be afraid of the chamber, and I was going to make sure I spoke regularly and just didn't get scared of it". Since her first question at prime minister's questions – asking Tony Blair if it was time "to say goodbye to the Punch and Judy style of PMQs" – she has spoken up on everything from foreign affairs to the over-packaging of Easter eggs, and is now deputy leader of the Scottish Liberal Democrats.

"So," she continues, "you know, when I went to Chechnya in 2010, and looked at the human rights situation, I think I arg-u-ably," she spaces out the syllables to give just the tiniest hint of sarcasm, "felt more strongly about that". She straightens up in her seat. "But [airbrushing] is a very important issue. It's important because it has an impact on health. The Royal College of Psychiatrists has said very clearly that they think excessive retouching – and I would talk about this in a much wider context anyway, because it's not just about retouching cosmetics adverts, it's about the whole range of body image pressure on men and women – but this kind of culture creates a huge amount of pressure on people, and that can lead to self-esteem problems. At extreme ends, we have rising rates of eating disorders, and we [also] have a much larger section of the population that engages in what they would call disordered eating rather than eating disorders. And then, from an educational point of view, there's research that shows young people are less likely to participate actively in class on days when they're not feeling confident about their appearance."

She started working on this area in 2009, when it was part of a Lib Dem women's policy paper. She co-founded the Campaign for Body Confidence in March 2010, then became a leader of the all-party parliamentary group on body image in 2011. She says the campaign has "ambitious goals – to change the culture we're living in". What does she say to suggestions that body image isn't an appropriate area for politicians? "Well, it's not just politicians who are involved. After the policy paper was published … I was contacted by lots of organisations, and so, on the Campaign for Body Confidence, we have Girlguiding, the eating disorders association Beat, Mumsnet, Susie Orbach and her AnyBody team, YMCA, All Walks Beyond the Catwalk, and political representation too."

The all-party group has been hearing evidence from experts over the past months. One interesting snippet came from an industry voice who said that what had been acceptable in advertising 12-15 months ago was not any longer, due to public pressure, so maybe Swinson's incremental, small-scale system of complaints is working. I ask what other measures Swinson thinks politicians can take to address body-image problems. There's a possibility of education on this issue becoming a part of the PSHE curriculum, she says; there's also the question of "What do you do about parents? So much of what young people perceive about their body image is taken from watching their parents … I think we need to look at ways we can help parents pass on more positive messages to their children, and perhaps some of that can be done through health visitors, for example."

Another problem for young women, she says, is the paucity of strong women in the public eye. She and some other MPs are meeting with the head of sports at the BBC soon to discuss the fact that 2011's Sports Personality of the Year shortlist featured 10 men and no women. I ask whether there is any embarrassment in talking about this issue when there are only seven women Lib Dem MPs – just 12% of the party's total. The representation of women in the Lib Dems has long been disastrous – although not as disastrous as the fact that they have not a single non-white MP – and last year a report suggested they could potentially be left with no women MPs at all after the next election. Five of their women MPs are in marginal seats, including Swinson.

Swinson has opposed all-women shortlists in the past – at the 2001 Lib Dem party conference she wore a bright pink T-shirt saying I Am Not a Token Woman – but it's these shortlists that led to a sea-change in the representation of women in parliament: the breakthrough moment in 1997 when 101 female Labour MPs were elected. She speaks enthusiastically about the Lib Dem's leadership programme, which involves mentoring people from under-represented groups, but, speaking to experts in this field, there is scepticism about whether this will make much difference.

In many ways, Swinson is impressive, and the Lib Dems could do worse than to promote her – she is articulate, loyal, always willing to put her head above the parapet, and in a way that draws the focus to the issues rather than her as an individual. She is confident, a comprehensive school pupil who loved debating and went on to study management at the London School of Economics. But her devotion to politics can sometimes make it difficult to find out if there's much beneath the rhetoric. I ask about growing up in Milngavie, part of the area she now represents, and rather than any insight into her childhood, she talks about it being a middle-class, affluent area, with "a lot of community spirit and social capital, so the list of groups doing fantastic things is as long as your arm". This analysis goes on for some time.

Her family wasn't particularly political, she says – her mother is a primary school teacher, father was in economic development – but she realised she was passionate about politics, and about the Liberal Democrats, when she stayed up all night during the 1997 election, months before she was actually eligible to vote. She joined the party at her university's freshers' fair, spurred, she says, by two key issues: education and proportional representation.

It must have been a bruising experience in government so far, given the rise in university tuition fees (Swinson was one of 28 Lib Dem MPs who voted in favour) and the disastrous vote on AV? "Well, do you know what, I'm a democrat as well," she says, "so I campaigned hard on AV, but the people have the say at the end of the day … And as Vince [Cable]'s PPS [principal private secretary] I was very involved in seeing how we improved the situation [regarding tuition fees]. We made sure that there was a cap on fees, which there wouldn't have been without us." In some ways, she just seems thrilled to be in government, to be able to make changes to policy, however small – rather than battling from the opposition benches.

I put it to her that some people would see the focus on body confidence as an easy way for the government to appeal to the women's vote without actually spending money – a cheap sop for the ladies. She is unruffled, and points out she has been campaigning on the issue since 2009, and never expected to be doing so within government. "Yeah, much of the action we're taking isn't going to cost a lot, because there isn't a lot of money around. It would be great [if there was] – you could propose all sorts of things, but there's a point in being realistic about it and saying, 'Well, if there isn't loads of money, then what can we do that isn't going to cost a lot?'"

It's a practical approach, I suppose, and frustrating, too. I hope Swinson's campaign causes a shift in the culture, and I'm glad she's working with such great organisations. But with so few women in government, it can't help but feel a slightly odd time to be prioritising this above so many other concerns she could be pouring her undisputed energies into. Feeling good about your body is a boon, but it rarely beats a steady job.